Current limit acceleration relay



CURRENT LIMIT ACCELERATION RELAY Filed Oct. 18, 1934 a 26 L 4/ i 0 47 F a p 28 A 23 46 k A 34 4 36%. (L g g 35 20 a d 37 22 /9 Wn'NESSES:

INVENTOR W, Edwin S f/o/jman.

0 1 a BY ATTORNEY Patented Sept. 7, 1937 UNITED STATES PATENT OFFICE CURRENT LIMIT ACCELERATION RELAY Application October 18, 1934, Serial No. 748,844

13 Claims.

My invention relates to electromagnetic devices and particularly to relays for protecting electric circuits.

To better understand the novel features and objects of my invention, a brief description of the prior art and the practice heretofore in vogue is necessary. Current-limiting accelerating relays, as heretofore proposed and still in use, are provided with a series coil, similar to that hereinafter described for my invention, but in order that the relay may effect its controlling action, the accelerating contactor controlled by such relay is provided with a tail piece on the armature for mechanically releasing the relay contacts of the succeeding relay when the previous accelerating contactor operates, thereby permitting the accelerating relay to drop to its contact making position when the current in the circuit to be controlled decreases to a predetermined value. Such a mechanical arrangement always requires that the accelerating relay be mounted directly below the accelerating contactor. Obviously, such arrangement likewise requires a longer and wider control panel, a requirement frequently very difiicult to satisfy.

Furthermore, by mounting the accelerating relay directly below the accelerating contactor, which frequently interrupts currents of considerable value, the relay is positioned at a place where considerable arcing takes place. This arcing, by virtue of the heat generated and the fumes nearly always present after there has been an arc, causes a deterioration of the contact members of the relay, which impairs the efiiciency of operation of the relay, makes it unreliable, and causes unnecessary maintenance expense, aside from the fact that the larger panel is also much more expensive than a smaller panel. Aside from the disadvantages just mentioned, the devices of the prior art involve complicated mechanical arrangements in that the relay must be definitely located and adjusted with respect to the contactor. This adjustment cannot be maintained due to the wear of the main contacts of the contactor.

It is an object of my invention to eliminate all of the above-discussed defects inherent in the devices of the prior art by the provision of electrical means for releasing the relay, thereby permitting the relay and the releasing'means to be mounted on separate control panels stationed at any convenient point remote from the accelerating contactors.

An advantage formyarrangement becomes very manifest when my type of relay is used to control the operation of large contactors. The contactors and relays may be mounted on separate panels so that the closing hammer action of the large contactors does not affect the relays to produce vibration and arcing, and thus result in faulty operation.

A further object of my invention is to provide a simplified electrical control and interlocking system between the accelerating relays and the accelerating contactors.

It is also an object of my invention to provide a current-limit accelerating relay which is simple, inexpensive and may be easily installed.

It is also an object of my invention to combine my novel current accelerating relay with a control system for an electric motor to thus more reliably and effectively control the operation of the motor.

Other objects of my invention will become more apparent from a study of the following specification taken in conjunction with the accompanying drawing, in which:

Figure 1 is a side elevational View of my relay, the view having certain parts broken away to show some of the details of the relay; and

Fig. 2 shows a motor starting control system utilizing the relay illustrated in Fig. 1.

Referring particularly to Fig. l of the drawing, my novel current-limit accelerating relay 60 has a U-shaped magnetic circuit structure 61 mounted on a suitable control panel 63. The magnetic circuit structure 6| has an L-shaped extension 65 which, together with a movable plunger-type armature 66 having an adjustable enlarged portion 61 at its lower end, forms a closed magnetic circuit.

It should be noted that relays l0 and 80 of Fig. 2 are identical with relay 60, so that only the latter need be described in detail.

The main magnetic circuit structure BI is provided with a stationary armature 68 rigidly secured in the middle portion of a brass sleeve Tl extending between the arms of the U-shaped structure BI, and also with a movable armature 62 located within the lower portion of sleeve H and subject to the controlling action of the series coil H, which may comprise a small number of turns of strap conductor wound in spaced relation around sleeve H and has its terminals insulated from but mechanically secured to the arms of U-shaped structure 6|.

The movable armature 62 extends through an opening in the lower arm of structure GI and is provided with an enlarged lower end portion 10 located below that arm, which enlarged end is surrounded by a spring 12, which tends to move an insulated contact member 24, located at the bottom of end portion 10, downwardly to make contact with two spaced contact members 25.

In the showing in Fig. 1, it is assumed that coil I? is fully energized, whereby the movable armature 62 is held in its upper position to engage the fixed armature'68, and thus hold the contact member 24 in a spaced relation with reference to the contact members 25 against the bias of the spring 12.

In order that the contact member 24 may be caused to descend for dilferent values of current in the series coil H, the relay is also provided with an adjustable armature 69, located in the upper portion of sleeve TI and having a screw .ing a coil l9.

threaded portion extending therethrough above the upper arm of U-shaped structure 6!, for varying the air gap 13 between the fixed armaturefit and the adjustable armature 69. It is obvious that a movement of the armature 69 in a'vertical direction will vary the efiective flux and thus the force that may be exerted on the movable armature 62. The adjustable armature 69 is shown as provided with a slotted head for ready adjustment and with a locking screw at the upper portion so that'the adjustment may not change, except when desired.

To prevent the closing of the contact member 24 and contact members 25 when not desired, a lift lever 23 is disposed below the contact member 24 and is adjustably'secured to the springbiased armature B6 of an 'electromagnet i hav- The armature 65 extends through the lower arm of U-shaped structure (it and is provided with a spring 2| which acts between that arm and the upper enlargedend of armature 66. The spring 2| normally holds the contact member 24 in the position shown regardless of whether coil I! is energized or not. The lower portion of armature 66 is provided with an adjustable enlarged'actuating portion 61 mounted within the influence of coil l9 which is provided with an internal copper tube 22 for delaying the movement of the lift lever 23 in the downward direction when coil I9 is energized. The utility of this arrangement will become more apparent from the study of thesequence of operation of a system of control utilizing my novel current-limitaccelerating-relay.

The control system shown in Fig. 2 utilizing my invention, includes a motor I3 having the field winding 2 and the accelerating-resistors l4,

l5 and i5. The accelerating resistors are disposed to be shunted by a plurality of currentlimit accelerating contactors 29, 42 and 54. These contactors are controlledby setup relays 64, ill and 80 respectively. Each of the relays is controlled in operation by an electromagnetic device such as is shown at ,15 in Figs. 1 and 2. A

line contactor 8, controlled by a starting switch 6 and a stop switch 9, is disposed to connect the motor I 3 to the buses I and 5.

Referring more particularly to Fig. '2, a shunt motor I3 is associated with accelerating resistors l4, l5 and I6, which resistors may be shunted by accelerating contactors 54, 42 and 29, respectively; To control these respective accelerating contactors current-limit accelerating relays 80, 1D, 60 are utilized. To start the operation of this system, the motor is provided with a line contactor 8. V

If it be assumed that buses or supply-circuit conductors and 5 are suitably energized from a source of direct-current energy, an energized circuit will be established from bus I through the shunt field winding 2 of the motor I3, and conductors 3 and 4 to the bus 5. The field winding 2 of the motor is thus energized and the opera tion of the motor may proceed at the will of the attendant. If the attendant actuates the normally open starting switch 6, a circuit is established from bus I through switch 6, actuating coil 1 of the line contactor 8, normally closed stop switch 9 and conductor ID to the bus 5.

Operation of the line contactor 8 immediately establishes a holding circuit for the coil 1 through contact members I l which bridge starting switch 6. The attendant may thereafter release switch 6 and the motor will continue in operation.

Substantially simultaneously with the closing of the contact members ll, contact member I2 closes, thereby establishing a circuit through bus i, contact member I2, armature of motor i3, resistor sections I4, l5 and I6, series coil I! of the current-limitaccelerating relay 60 and conductor 4 to the bus 5. Since a comparatively large current will flow through the armature of the motor at the start, the coil I! is highly energized, thereby holding the contact member 24 in the open position shown.

An instant after the closingv of contact member i2, loosely mounted contact member' E8 of line contactor 8 closes, thereby energizing coil E9 of the electromagnet '55, which controls contact member 24. Spring 2! which normally holds the armature in the position shown will be compressed and lift lever 23 will be pulled downwardly to release contact member 24. The copper tube 22 inside coil l9 provides some time delay in order to insure that contact member1 24 will be subject to the control of series coil H before coil 19 is energized.

Contact member 24 having thus been released, after the current in the motor circuit has decreased to a value determined by the position of the adjustable armature ,69 of accelerating relay 6!], contact member 24 will drop to establish a circuit from bus I through conductors 26 and 21, actuating coil .28 of the accelerating contactor 29, contact members 24 .and ,25-of the accelerating relay 6i] and conductor 39 to thebus 5. Operation of the accelerating contactor 29, upon this energization of its coil 28, closes contact member 3|,

thereby shunting resistorsection l6 and coil l1 and establishing an energizing circuit'for coil 32 through resistors 14 and 15. Contact member 33 will also be closed bythe operation of the accelerating contactor 29, thereby energizing coil .35 which will cause the lift lever, diagrammatically shown at 39, to release contact members 44 after a short interval of time as determined by the sleeve 36 and spring 31. v

The current in series coil 32 at thisstage of operation is,however, of considerable value, and contact -member 40 is retained in -the :position shown for aninterval of time requiredior a certain decrease of armature current in series coil 32 which, in turn, will be determined, in part, by the adjustment of an adjustable armature such asshown at 69inFig. 1.

After contact member 48 descends, .coil 4| of the accelerating-contactor 42 :is energized, thereby shunting the resistor section i5 and coil] 3-2 through coil 44 .and contact members 43. Further, closing of contact members .45 establishes an energizing circuit for the coilx46 of the last current-limit accelerating relay :80, which ;thus

:releases contact-1 members-5 [with :the {downward movement of lift lever 50. After a predetermined decrease in armature current traversing coil 44, contact member 5| descends, thus energizing coil 52 of the last accelerating contactor 54, which shunts the last resistor section l4 and coil 44. The motor is thus subject to full voltage and accelerates to full speed.

From the foregoing discussion, it is obvious that the current-limit accelerating relays 80, I0 and 80 may be mounted entirely apart from the rest of the control system, including their respective contactors, and these units may, therefore, not be subjected to contactor impact and it is also not necessary to maintain a definite mechanical relation between contactors and relays. The maintenance expense is thus decreased, the mechanical arrangement is very materially simplified, the cost of the control system is de creased, and above all the reliability and efiiciency of operation are enhanced.

I do not limit myself to the specific control system hereinshown, since my novel relay is equally usable with a system of control for an alternating-current motor or any system of control where a definite sequence of operation is to be controlled. In an alternating current release magnet constructed in accordance with my invention, suiiicient time delay is obtained by properly proportioning the magnet and taking advantage of the plunger principle which is 111- herently slow in operation. Nor do I limit myself to the specified structure of the current limit accelerating relay herein described, since it is obvious that others skilled in the art, after having had the benefit of the teachings of this invention can variously modify my invention without departing from the spirit and scope thereof. I Wish, therefore, to be limited only by the scope of the claims hereto appended.

I claim as my invention:

1. In a current-limit accelerating relay, in combination, a magnetic circuit including a frame, a fixed armature, an adjustable armature to vary an air-gap between the fixed armature and the adjustable armature, and a movable armature, a spring for biasing the movable armature to a given position, a lever, electromagnetic means coacting with said lever to hold said movable armature in a given position against the bias of said spring, and a coil for holding said movable armature in said given position against the bias of said spring.

2. In a relay, an operating element biased to a given position, a coil for holding said element in a position against said bias, means for assisting in so holding said element while permitting control by said coil to certain other positions, and electromagnetic means for releasing said element from said assisting means to thus subject said element to the control of said coil to additional positions also.

3. In a relay, an operating element, mechanical means for holding the element in a given position, electromagnetic means for holding the element in said given position upon energization of said electromagnetic means, other electromagnetic means for eliminating the effect of said mechanical means when said other electromagnetic means are energized, and control means for energizing said first-named electromagnetic means an instant before the energization of said other electromagnetic means.

4. In combination, in a relay, a movable armature, circuit connections controlled by said armature, control means for controlling the position of said armature, holding'means for fixing the position of said armature and adapted to permit for control by said control means to additional positions.

5. In a relay, the combination of a movable armature, circuit connections controlled by said armature, electromagnetic control means for controlling the position of said armature, holding means for holding the armature in a given position, electromagnetic means for releasing said holding means, means for energizing said lastnamed electromagnetic means, and means energizing said electromagnetic control means and thereafter energizing said last-named electromagnetic means.

6. In a relay, the combination of a movable armature, circuit connections controlled thereby, electromagnetic control means for controlling the position of said armature, means varying the control efi'ect of said control means, holding means for holding said armature in a given position, releasing means for releasing said holding means to thus subject the armature to the effect of said control means, and means for energizing said control means and only thereafter actuating said releasing means.

7. The combination of electric circuit means and control means therefor including a relay having a movable armature, control means responsive to certain electric characteristics of said means to control the position of said movable armature, holding means for mechanically holding the armature in a given position, means for eliminating the effect of said holding means to thus subject the armature to the action of said control means, and means responsive to certain operations of said armature to control the electric characteristics of said electric circuit means.

8. The combination of electric circuit means and control means therefor including a relay having a movable armature, electromagnetic control means responsive to certain electric characteristics of said circuit means to control the position of said movable armature, adjusting means for adjusting the efiect of said control means, holding means for holding the armature in a given position, electromagnetic means for eliminating the effect of said holding means to thus subject said movable armature to action of the control means, and means responsive to certain operations of said armature to control the electric characteristics of said electric circuit means.

9. The combination of an electric circuit means and a control system therefor, said system including a main switch for energizing the circuit means, a relay, a contactor interconnected electrically only with, and controlled by, said relay, said relay having means responsive to the current in said circuit means for delaying the operation of said contactor till the current has decreased to a selected value, and electromagnetic time-delay means energized by the operation of the main switch for releasing the relay controlling the contactor.

10. The combination of electric circuit means and control means therefor, said control means including a relay having contact means responsive to a current in said circuit means for controlling the arrangement of said circuit means, means for adjusting said contact means to cause the same to operate at any selected current in said circuit means, holding means for holding fsaidcontact means in a given position, electromagnetic means adapted to be energized after positions, electromagnetic means for releasing said element from said assisting means to thus subject said element to the control of said coil ;to additional 1 positions also, and time-delay means for delaying the releasing operation of said electromagnetic means.

12. In combination with a relay, a movable armature, circuit connections controlled by said armature, control means for controlling the position of saidarmature, holding means for fixin g the position of said armature and adapted to permit control by said control means to certain other positions, releasing means .for eliminating the effect of said holding means to thus release the armature for control by said control means to additional positions also, and time-delay means for delaying the operation of said releasing means. 7 a

13. In a relay, :the combination of 'a movable armature, circuit connections controlled thereby, control means for controlling the position of said armature, means for adjusting the effect of said control means, holding means for holding said armature ina given position and adapted topermit control by said control means to certain other;

positions, releasing means for-eliminating the efiect of'said holding means ,to thus release the armature for control by said control means to additional positions also, and time-delay vmeans for delaying the operation of said releasing a means.

EDWIN SUMNER HOFFMAN. 

